Physical limnology of Italian lakes. 2. Relationships between morphometric parameters, stability and Birgean work

The relations of morphometric parameters with maximum stability (S) and maximum Birgean work (B) are analysed for 31 Italian lakes. Results show that in deep lakes the depths are more correlated with S, while fetch is more correlated with B. In contrast, in shallow lakes the depths are correlated both with S and B, while the correlation with fetch is insignificant. Power regressions are used to define the relation between maximum depth, S and B, and an analysis is made of lakes showing a marked deviation from the curves, whether on account of their environmental features or their internal hydrodynamic state. In meromictic lakes total stability is subdivided into chemical and thermal stability; major inferences are made as to the depth of their winter mixing. The relationship between B and maximum depth is less significant than that between zmax and S, as lakes with depth >100 metres and therefore with a very thick hypolimnion do not fully satisfy the regression function. Lastly, heating efficiency (E) is evaluated and related to depth and surface area of the lakes; the conclusion is that shallow lakes are more efficiently heated than deep ones.